I have been using a twisty one, that you have to bend in a figure of eight to unlock, as a keyring for a few years now, without problems. They don't come unscrewed because they don't use a screw mechanism. I've not had any issues with the wire becoming frayed with these (but I have with the screw-based ones). They are coated with nylon, but I think they are just made with different wire to the screw-based ones.

See for example MrLock (not a recommendation, just the first link I found to illustrate the product).